The U.N. peacekeeping mission in Congo reported that suspected fighters from the Allied Democratic Forces (ADF), a Ugandan Islamist group, raided the village of Luna, north of Beni in North Kivu province, said Stephane Dujarric, spokesman for the U.N. Secretary General.

"The U.N. mission is deploying a fact-finding mission to gather more details about this horrific incident," he said, adding that 1,500 people fled towards Ituri province in the wake of the attack.

Eastern Congo has been plagued by instability and conflict for two decades and civilians are often the target of militia, rebels and military units. Competition for the region's mineral resources has helped fuel the fighting.

There were at least 17 victims including eight women and four children who were shot and hacked to death, said the Centre of Study for the Promotion of Peace, Democracy and Human Rights (CEPADHO), which documents violence in North Kivu.

The raid on Luna took place 300 meters from two U.N. mission bases, Omar Kavota, executive director of CEPADHO, said in a statement, adding that seven of the dead were from one family.

An American researcher on Congo reported in April that soldiers had taken part in massacres of civilians in northeastern Congo since 2014.

The Kinshasa government has blamed most of the killings on the ADF, which has operated in the area since the 1990s.

The government subsequently expelled the researcher, Jason Stearns.

Political tensions are high in Congo, where President Joseph Kabila, in power since 2001, is required by the constitution to step down before the end of the year.